Wind-Tunnel and Field Measurements of Particle–Turbulence Interactions
Conf’luence Martin Obligado
Professeur à l’ecole Centrale de Lille
Laboratoire de mécanique des fluides de Lille
Vendredi 13 février à 10h30 • Amphithéâtre Nougaro
Turbulent particle-laden flows are ubiquitous in both natural and industrial contexts. Among the many manifestations of particle–turbulence interactions, two phenomena have attracted sustained attention over recent decades: preferential concentration and the modification of particle settling velocity. Preferential concentration refers to the tendency of inertial particles to form clusters and voids within the flow, while settling modification concerns the enhancement or reduction of particle fall speeds under gravity with respect to stagnant conditions. Despite extensive research, current modelling capabilities remain limited, and even fundamental aspects of these processes (such as whether small spherical particles settle faster, slower, or at the same rate in turbulence compared with a quiescent fluid, and how particles are statistically distributed in space) are still not fully understood.
In this seminar, I will present recent wind-tunnel experiments designed to shed light on these issues. By employing a range of turbulence-generating grids, including both passive and active configurations, we explored a broad spectrum of inflow conditions and particle inertias, encompassing homogeneous isotropic turbulence and sheared flows. Preferential concentration and settling velocities were characterised using high-speed imaging and phase-Doppler particle analysis, respectively. The results highlight the central role of large-scale turbulent motions in governing both phenomena and are discussed in relation to existing theoretical and modelling frameworks. Finally, these results are used to characterise a series of rainfall events under field conditions, obtained near a wind farm located in the Pays d’Othe region.
